Conventionally, as disclosed in, for example, Japanese Patent Application Publication No. 2008-269487 (JP-2008-269487 A), in an engine control electronic control unit that is equipped with a microcomputer that adopts at least one of a multicore configuration and a cash memory mounting configuration, an art for reducing the power consumption during the stop of an engine is disclosed. Both CPU cores and a cash memory are elements with large power consumption in the microcomputer. Thus, in the aforementioned conventional art, a mode in which a maximum processing capacity is exerted by fully using the CPU cores and the cash memory is selected during the operation of the engine. A mode for setting the number of CPU cores and the used amount of the cash memory smaller than during the operation of the engine is selected during the stop of the engine.